The protection panel as noted above is provided in an electronic device such as a mobile phone, a smartphone, a PDA, car navigation equipment, a digital camera, a digital video camera, a portable gaming device, and a tablet, for example, to allow the user to perform a touch input operation in response to a display while protecting a display part of a display device provided in the electronic device.
Some recent models of the mobile phone and smartphone which are the examples of the electronic device having the above-noted protection panel include a texting function and an Internet function in addition to the original phone function, and further a photographing function and a music playback function. With such a multifunctional electronic device, it has been considered to improve the operability by providing a switch that is operable in response to those functions in the protection panel.
The protection panel of the above-noted type typically includes a plurality of function keys (switches) having a plurality of first contacts that are arranged electrically in m rows and n columns (M≧2, N≧2) in matrix, and a plurality of second contacts that are arranged to face the first contacts, correspondingly, in which the units of the first contacts arranged in a Y-axis direction are connected, per unit, to different points defined in an X-axis direction of a first surface resistive element (resistance film), while the units of the plurality of second contacts arranged in the X-axis direction are connected, per unit, to a plurality of (two) third terminals (electrodes) (see Patent Document 1, for example).
Another example of the protection panel includes a plurality of additional input sections (switches) in which a first conductive panel (front substrate) and a second conductive panel (back substrate) are connected to each other so that a first input area of a first transparent electrode (resistance film) provided in the first conductive panel faces a second input area of a second transparent electrode (resistance film) provided in the second conductive panel at a predetermined distance, and a third input area of the first transparent electrode provided in the first conductive panel faces at least one of a pair of second bus bars provided in the second conductive panel with a predetermine gap (see Patent Document 2, for example).    [Patent Document 1] Japanese Unexamined Patent Application Publication No. 9-44289    [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2002-202849